Purification and characterization of a thermostable trehalose synthase from Thermus aquaticus

Thermostable trehalose synthase, which catalyzes the conversion of maltose into trehalose by intramolecular transglucosylation, was purified from a cell-free extract of the thermophilic bacterium Thermus aquaticus ATCC 33923 to an electrophoretically homogeneity by successive column chromatographies. The purified enzyme had a molecular weight of 105,000 by SDS-polyacrylamide gel electrophoresis and a pI of 4.6 by gel isoelectrofocusing. The N-terminal amino acid of the enzyme was methionine, The optimum pH and temperature were pH 6.5 and 65 degrees C, respectively. The enzyme was stable from pH 5.5 to 9.5 and up to 80 degrees C for 60 min, The trehalose synthase from Thermus aquaticus is more thermoactive and thermostable than that from Pimelobacter sp. R48. The yield of trehalose from maltose by the enzyme was independent of the substrate concentration, and tended to increase at lower temperatures, The maximum yield of trehalose from maltose by the enzyme reached 80-82% at 30-40 degrees C. The activity was inhibited by Cu2+, Hg2+, Zn2+, and Tris.